The Ignition module (ECM) has to see the Battery negative, from case to apron to battery.
Every good-working module that I have ever tested, will give a spark out the coil-wire, when the ignition switch is turned from run to off. I call this the one spark test. If yours does this, then this leaves only a few potential candidates for a no spark while cranking situation. They are:
the Magnetic pick-up has failed
the distributor mainshaft is Not spinning
the reluctor gap is too large,
the reluctor has become magnetized
